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Study of the contribution of cooling systems

 

Study of the contribution of cooling systems that combine wetting and ventilation along feed bunks

 

I. Flemenbaum[1] and A. Ezra[2]

 

[1] Extension Service, Cattle Department, Ministry of Agriculture and Rural Development, Israel

[1] Israel Cattle Breeders’ Association

 

A study of cooling systems that combine wetting by garden sprinklers with artificial ventilation in the food alley area showed that optimal operation of cooling in the summer led to a production level that is 98% higher than the production level achieved in winter, and a fertility rate that is double the fertility rate in herds that are not cooled. A similar cooling system has recently been developed in Israel. In this system, the garden sprinklers are replaced by a cluster of four low-volume misters installed in front of each fan. Use of this system may lead to reduction of pollution caused by the cooling. In the past, we presented the results of experiments that were conducted in commercial dairy farms in the south of Israel. The efficiency of the misting system along the feed bunks was compared to the efficiency of the system that integrates wetting with garden sprinklers. Results of the comparison showed that both systems have a similar degree of effectiveness in reducing the decline in milk production and the reproduction rate in the summer. The objective of this study is to support the results of these experiments in a large number of herds with the aim of establishing knowledge on the subject in order to provide dairy farmers with recommendations.

The survey was conducted in the summer of 2003, and included two parts. Part A covered 10 collective dairy farms. In five dairy farms, the cooling system included wetting with a cluster of four misters (28-56 l/h discharge) installed in front of each fan. In the other five dairy farms, a similar cooling system was used, with wetting achieved by garden sprinklers (100-300 l/h discharge) that were installed above the cows’ backs along the feed alley. In both groups, the cooling system was operated along the feed bunks 4-5 times a day for a period of 30-45 minutes each time, after the cows returned from the holding pen. The holding pen was also cooled for 30-45 minutes each time, before and between milking.  Accumulated cooling time was 6-8 hours a day.

Part B examined the cooling effectiveness using the cluster system of misters in the family farm. The cooling system was similar to that in the parallel group in part A, in four family dairy farms in different areas. Cooling contribution was examined by comparing production and reproduction performance of the cows in these farms to the average performances of cows in the other dairy farms (a total of 24 herds participated in the survey). Analysis of both surveys was based on data in the Herd Book. The indices examined were: production performance (kg milk/cow/day) and fertility (conception rate from the first two inseminations). The data was processed using a GLM multifactor analysis of variance with SAS software. The factors in the “milk model” were: the treatment, the herd (in each treatment), number of lactations, lactation days, the season, and the interactions. The factors in the “reproduction model” were: the herd (in each treatment), the treatment and the insemination month.

Results of Part A (collective dairy farm): Table 1 presents a comparison of the production performance (kg/cow/day) and fertility (conception rate from the first two inseminations) of heifers and cows in both treatments, in the summer and winter months, the difference and the ratio between them. No difference was found between treatments in production and reproduction performance  . In all the herds, the summer-winter production ratio in terms of milk stood at 96% - 98.5% and in terms of (Economical Corrected Milk) ECM yield at 92.5% and 93% in the misting and sprinkling farms respectively. The range of summer-winter production ratio in the different herds was found to be similar in both treatments and fluctuates between 90% and 100% in milk production and between 88% and 98% in ECM yield.

Table 1: Productivity and fertility of cows and heifers that were studied (collective dairy farm)

 

First lactation

Adult Cows

Treatment

Misting

Sprinkler

Misting

Sprinkler

Milk production (kg/cow/day)

Summer

34.1

33.4

40.5

41.9

Winter

35.3

33.7

42.3

43.0

Winter-summer Difference

1.2

0.3

1.8

1.1

Winter –summer  ratio

97%

99%

96%

97%

Conception  % (number of inseminations in brackets)

Summer

40 (173)

46 (294)

36 (206)

36 (366)

Winter

55 (148)

45 (154)

43 (361)

36 (479)

Results of Part B (family dairy farm).

Table 2 presents a comparison of the same indices in family herds, with and without cooling, in summer and winter months, the difference and the ratio between them.

Table 2: Production levels and fertility of cows and heifers that were studied (family dairy farm)

 

First lactation

Adult Cows

Treatment

With cooling

Without cooling

With cooling

Without cooling

Milk production (kg/cow/day)

Summer

29.6

27.5

34.7

32.2

Winter

30.0

29.0

35.9

34.3

Difference winter-summer

0.4

1.5

1.2

2.1

Winter-summer ratio

99%

95%

97%

93%

Conception % (number of inseminations in brackets)

Summer

36 (30)

20 (126)

35 (47)

22 (213)

Winter

47 (57)

48 (192)

46 (136)

36 (483)

Cooling significantly improved the cows’ production and reproduction performance in the summer (P<0.01). In all the herds, the summer-winter production ratio in terms of milk ranged between  98% and 94%, and in terms of ECM yield  95% and 90%, in farms with and without cooling, respectively.

The study that is presented in this paper supports the findings of previous experiments that we conducted. The use of misters installed in  front of fans for wetting the cows  was found to have a similar degree of effectiveness as the use of garden sprinklers. Cooling the cows with both methods led to a summer production that exceeded winter production by over 97%, and pregnancy rates that were 35% higher, which allows distribution of calving in the herd. The large and similar variation  in production ratio between seasons , between herds within each cooling method indicates that the way that the system is installed and operated is the most important factor in cooling success, and is more important than selection of the system chosen for cooling the cows. Use of misting may have a certain advantage in that it can allow effective cooling, with less wetting of lanes and reduced pollution of the area, a fact that have much importance using cooling system in many herds in Israel and all over the world.



[1] Agricultural Extension Service, Cattle Department, Ministry of Agriculture and Rural Development, Israel

[2] Israel Cattle Breeders’ Association